How to tell if teeth/gums are weak?

How can you tell if an acid, base and salt is strong/weak?

• I have a chemistry exam coming up soon and I still can't tell how you know which acid or base is strong or weak by just looking at their chemical formula. I know that if it has complete ionization, then it's a strong acid. Say I was given a salt like KBr, how can I tell whether it is a acidic, basic or neutral salt?

• Answer:

  EDIT: I'VE RECTIFIED AN ERROR! Okay, as you probably know, a strong acid and a strong base are those which undergo complete dissociation in water. Let's take HCl and NaOH as examples: HCl(aq)→H⁺(aq)+Cl⁻(aq) NaOH(aq)→Na⁺(aq)+OH⁻(aq) A weak acid and a weak base are those which undergo partial dissociation in water. Let's take CH₃COOH and NH₃ as examples: CH₃COOH(aq)↔H⁺(aq)+ CH₃COO⁻(aq) NH₃(g)+H₂O(l)↔NH₄⁺(aq)+OH⁻(aq) If you had a 1M sample of HCl and a 1M sample of CH₃COOH, the pH of HCl would be lower since all the HCl molecules dissociate while only about 1% of the CH₃COOH molecules dissociate. Therefore, [CH₃COOH] would have to be about 100 times that of [HCl] to yield the same pH value/[H⁺]. As for salts, a salt is a compound formed when the H⁺ ion in an acid is replaced with a metal ion or ammonium ion. In order to determine whether a salt is acidic, basic or neutral, it's important to look at the anion and then imagine it attached to H⁺. If the acid from which the salt was formed is a strong acid which reacted with a strong base, then the salt is neutral(eg NaCl from HCl+NaOH). If the acid from which the salt was formed is a weak acid which reacted with a strong base, then the salt is weakly basic(eg CH₃COONa from CH₃COOH+NaOH) . If the acid from which the salt was formed is a strong acid which reacted with a weak base, then the salt is weakly acidic(eg NH₄Cl from NH₃+HCl). In the case of KBr, the original acid was HBr(a strong acid) and the original base was KOH(a strong base). Therefore, KBr is a neutral salt. All halide salts are neutral except for fluoride salts since HF is a weak acid. I hope this helps and feel free to send me an e-mail if you have any doubts!